Despite the notoriety of Ebola virus disease (EVD) as one of the world’s most deadly infections, EVD has a wide range of outcomes, where asymptomatic infection may be almost as common as fatality. With increasingly sensitive EVD diagnosis, there is a need for more accurate prognostic tools that objectively stratify clinical severity to better allocate limited resources and identify those most in need of intensive treatment. This retrospective cohort study analyses the clinical characteristics of 158 EVD(+) patients at the GOAL-Mathaska Ebola Treatment Centre, Sierra Leone. The prognostic potential of each characteristic was assessed and incorporated into a statistically weighted disease score. The mortality rate among EVD(+) patients was 60.8% and highest in those aged 25 years (p<0.05). Death was significantly associated with malaria co-infection (OR = 2.5, p = 0.01). However, this observation was abrogated after adjustment to Ebola viral load (p = 0.1), potentially indicating a pathologic synergy between the infections. Similarly, referral-time interacted with viral load, and adjustment revealed referral-time as a significant determinant of mortality, thus quantifying the benefits of early reporting as a 12% mortality risk reduction per day (p = 0.012). Disorientation was the strongest unadjusted predictor of death (OR = 13.1, p = 0.014) followed by hiccups, diarrhoea, conjunctivitis, dyspnoea and myalgia. Including these characteristics in multivariate prognostic scores, we obtained a 91% and 97% ability to discriminate death at or after triage respectively (area under ROC curve). This study proposes highly predictive and easy-to-use prognostic tools, which stratify the risk of EVD mortality at or after EVD triage. The unprecedented spread of EVD across the fragile healthcare systems of West Africa during the 2013–2015 outbreak infected over 28,600 patients and established it as a disease for which low-income countries are at disproportionate risk. In order to improve the standard of patient care, it is essential to better allocate scarce resources amongst the heterogeneous symptomatic presentations of EVD. This retrospective cohort study on 158 EVD(+) patients in Sierra Leone constructs 2 easy-to-use scoring systems that accurately stratify EVD severity and thus objectively identify the patients in most need of intensive therapy. Using statistically weighted symptoms and demographic characteristics, we obtained scores with a 91% and 97% ability to discriminate death at or after triage respectively. These scores included Ebola viral load, patient age and referral time as well as the symptoms of disorientation, haemorrhage and myalgia. Further univariate analysis revealed several independent predictors of mortality, where patients aged between 5 and 25 years were most likely to survive, while malaria co-infection increased the risk of death by 2.5-fold (p = 0.01). Correcting referral-time for viral load, we also quantify the benefits of early reporting as a 12% mortality risk reduction per day (p = 0.012). Mortality in this cohort was 3-fold more than patients treated in resource-rich settings (60.8% vs. 18%) and we propose that focused patient care is a feasible and low-cost effort that may begin to close this gap.